Algebraic effect handlers, introduced by Plotkin and Power in 2002, are recently gaining in popularity as a purely functional approach to modeling effects. In this article, we give a full overview of practical algebraic effects in the context of a compiled implementation in the Koka language. In particular, we show how algebraic effects generalize over common constructs like exception handling, state, iterators and async-await. We give an effective type inference algorithm based on extensible effect rows using scoped labels, and a direct operational semantics. Finally, we show an efficient compilation scheme to common runtime platforms (like JavaScript) using a type directed selective CPS translation.

I am a member of the Research In Software Engineering (RISE) group and chair of the Programming Languages working group (PLX). Currently, I am interested in the design and application of strong type systems and declarative programming languages, like Haskell. In particular, I am interested in programming with Effect inference in the Koka project. Furthermore, I work on domain specific embedded languages, language design, and compiler technology.